A £198m hypersonic drone designed to travel twenty times the speed of sound overheated and dismantled in the middle of its test flight before crashing into the ocean, the Pentagon has revealed.

An artist’s impression of the test flight (Picture: AFP)

An artist’s impression depicts the hypersonic weapon’s final moments before it crashed to earth as it travelled over the Pacific Ocean last summer.

The Pentagon’s drone was designed to fly explosives anywhere in the world within an hour but broke up over the Pacific during testing after travelling at speeds of 21,000kph (13,000mph).

It could not cope with generated temperatures exceeding almost 2000C, causing it to crash into the ocean, officials confirmed.

Despite the drone failing to reach its target, an official for the Defence Advanced Research Projects Agency insisted there were some positives to take from the test flight.

‘The initial shock wave disturbances experienced… from which the vehicle was able to recover and continue controlled flight, exceeded by more than 100 times what the vehicle was designed to withstand,’ DARPA acting director Kaigham J Gabriel said.

‘That’s a major validation that we’re advancing our understanding of aerodynamic control for hypersonic flight.’